NWA 6163 (prov.) - for sale

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NWA 6163 (prov.)
Iron (ungrouped)
Find: 2008
Northwest Africa
TKW 358g

History: A single iron mass was purchased from a Moroccan dealer in October 2008 by M. Graul (Bernau, Germany).

Physical characteristics: The 358 g mass, measuring 70 x 57 x 35 mm, has a cone-like shape with a surface roughly flat and one more convex. The external surface of the meteorite is partially (> 50%) covered by a brown fusion crust and presents several roughly circular depressions up to 1 cm in diameter.

Petrography: (M. D’Orazio, DST-PI) Etched sections show a well-preserved heat-affected rim and a peculiar internal structure of sub-equant, 5-10 mm kamacite grains with prominent Neumann bands between which are comb-net plessite bodies. Troilite occurs within kamacite as 1-6 mm rounded inclusions showing lamellar twinning, whereas schreibersite forms 100-500 mm subhedral elongated crystals often grown at the troilite-kamacite interface. Several inclusions of troilite show, towards their contact with the host kamacite, replacements by chalcopyrite. Many small hollow spaces (from 0.5 to 10 mm in length), sometimes lined with black iron hydroxides, characterize the internal structure of this meteorite. Close to the external surface these cavities are filled with rounded, sand-sized, grains of quartz from the desert soil.

Geochemistry: Composition of the metal (ICP-MS; D’Orazio and Folco 2003) is Co = 0.427, Ni = 8.43 (both in wt%), Cu = 258, Ga = 15.1, Ge = 54.3, As = 11.1, W = 1.55, Re = 0.48, Ir = 4.2, Pt = 9.6, Au = 1.08 (all in ppm).

Classification: Iron meteorite, ungrouped, with anomalous structure.

Type specimen: a 27.7 etched endcut and a 11.8 g etched full slice are on deposit at DST-PI. M. Graul holds the main mass.

Ref.: D’Orazio, M. and Folco, L. (2003). Chemical analysis of iron meteorites by inductively coupled plasma – mass spectrometry. Geostandards Newsletter, 27, 3, 215-225.

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